High-quality X-rays can be used for applications ranging from analyzing the structure of matter to advanced medical imaging. State-of-the-art X-ray sources can now produce coherent high-brightness X-rays of greater than kiloelectronvolt energy and promise a new revolution in imaging complex systems on nanometer and femtosecond scales.
X-rays are generated by means of Compton scattering through the collision of photons with energetic electrons.
Previous devices that have been utilized for such generation of X-rays comprise a high peak power laser that produces X-rays when a beam from the laser interacts with an electron beam in a vacuum environment. See P. Sprangle, A. Ting, E. Esarey, and A. Fisher, “Tunable, short pulse hard xrays from a compact laser synchrotron source,” J. Appl. Phys. 72, 5032 (1992); see also A. Ting, R. Fischer, A. Fisher, K. Evans, R. Burris, J. Krall, E. Esarey, and P. Sprangle, “Observation of 20 eV xray generation in a proof of principle laser synchrotron source experiment,” J. Appl. Phys. 78, 575 (1995). In such previous systems, the electron beam is generated by either a radio frequency linear accelerator or by another laser beam that counter-propagates with the first one.
However, aligning a laser beam with a counter-propagating electron beam is very difficult. Moreover, the length of the X-rays generated by such prior art devices is limited by the distance (usually measured in micrometers) of overlap between the laser beam and the counter-propagating electron beam.